Article sortation systems are known and include a plurality of transport units which are movable along a conveying path between a package induct station and a discharge station or port. Some article sortation systems, known as carousel sorters, travel in a generally horizontal closed circuit. Some carousel sorters include crossbelt transport units, which are able to handle parcels of widely varying characteristics. For example, such systems may be used to sort magazines or envelopes at a postal center, frozen food articles, cellophane wrapped clothing articles, or the like. The crossbelt sortation systems are widely adaptable because the parcels are loaded onto article supports or carrier belts of the transport units. The carrier belts are movable generally perpendicular to the conveying path of the transport units, and the parcels are discharged from the units via movement of the carrier belts, after the transport unit has carried the parcel to the appropriate destination along the conveying path. Another example of carousel sorters include tilt tray sorters.
Parcels may be inducted to the transport units at various separate locations using a plurality of induction stations. However, only one package may be inducted from a given induction station onto a given transport unit at any time. If multiple induction stations are implemented, the throughput of the system may not be significantly enhanced unless one or more discharge stations are positioned between the induction stations to allow at least some of the transport units to empty their packages before arriving at the second induction station. Otherwise, a package may remain on a transport unit as it passes the second induction station, thereby precluding the transport unit from receiving another package at the second induction station.
Some crossbelt conveyor units can receive two packages on the belt of the conveyor unit. The objects, or packages, may then be discharged at appropriate stations. However, in order to properly position the packages at the appropriate side of the conveyor units, the packages need to be properly arranged and sequenced prior to being inducted onto the conveyor units. This requires an additional process of presorting the packages, which reduces the efficiency of the crossbelt sortation system.